package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import com.hmdp.utils.SystemConstants;
import org.springframework.data.geo.Distance;
import org.springframework.data.geo.GeoResult;
import org.springframework.data.geo.GeoResults;
import org.springframework.data.redis.connection.RedisGeoCommands;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.domain.geo.GeoReference;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = cacheClient.queryByIdWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.SECONDS);

        //互斥锁解决缓存击穿
//        Shop shop = queryByIdWithMutex(id);
        Shop shop = cacheClient.queryByIdWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        return Result.ok(shop);
    }

    public void saveShop2Redis(Long id, Long expireSeconds){
        Shop shop = getById(id);
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY+id, JSONUtil.toJsonStr(redisData));

    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public Shop queryByIdWithLogicExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
        // 从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            return null;
        }

        //命中，需要先把json反序列化
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            // 未过期，直接返回
            return shop;
        }

        // 已过期，缓存重建     
        // 获取互斥锁
        String lockkey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockkey);
        try {
            if (isLock) {
                // 成功，开启独立线程，实现缓存重建查询数据库
                // TODO  注意：获取锁成功后要再次检查redis缓存是否过期。如果缓存存在，则无需重建缓存
                CACHE_REBUILD_EXECUTOR.submit(() -> {
                    this.saveShop2Redis(id,20L);
                });
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            unLock(lockkey);
        }
        //返回过期商铺信息
        return shop;
    }

    public Shop queryByIdWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        // 从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            // 存在直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return  shop;
        }

        //判断命中的是否是空值
        if (shopJson != null) {
            return null;
        }

        // 不存在，根据id查询数据库
        Shop shop = getById(id);


        // 实现缓存重建
        try {
            // 1.获取互斥锁
            boolean lock = tryLock(LOCK_SHOP_KEY+id);
            // 2.判断是否获取成功
            // 3.如果失败，休眠并重试
            if (!lock) {
                Thread.sleep(50);
                return queryByIdWithMutex(id);
            }

            // 4.成功，根据id查询数据库
            // 模拟查询数据库的延迟
            Thread.sleep(100);
            if (shop == null) {
                //将空值写入redis---->防止缓存穿透
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }

            // 存在，写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            // 5.释放互斥锁
            unLock(LOCK_SHOP_KEY+id);
        }

        return shop;
    }

    public Shop queryByIdWithPassThrough(Long id) {
        String key = CACHE_SHOP_KEY + id;
        // 从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            // 存在直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return  shop;
        }

        //判断命中的是否是空值
        if (shopJson != null) {
            return null;
        }

        // 不存在，根据id查询数据库
        Shop shop = getById(id);

        // 不存在，返回错误
        if (shop == null) {
            //将空值写入redis---->防止缓存穿透
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        // 存在，写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);

        return shop;
    }

    //获取锁
    public boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10L, TimeUnit.MINUTES);
        return BooleanUtil.isTrue(flag);
    }

    // 释放锁
    public void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id == null){
            return Result.fail("店铺id不能为空");
        }
        String key = CACHE_SHOP_KEY + id;
        //更新数据库
        updateById(shop);
        //删除缓存
        stringRedisTemplate.delete(key);


        return Result.ok();
    }

    @Override
    public Result queryShopByType(Integer typeId, Integer current, Double x, Double y) {
        //判断是否需要根据坐标查询
        if(x == null || y == null){
            //不需要坐标，直接数据库查询
            Page<Shop> page = query().eq("type_id", typeId).page(new Page<>(current, SystemConstants.DEFAULT_PAGE_SIZE));
            return  Result.ok(page);
        }
        //计算分页参数
        int from = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
        int end = current * SystemConstants.DEFAULT_PAGE_SIZE;
        //查询redis、按照距离排序、分页
        String key = SHOP_GEO_KEY + typeId;
        GeoResults<RedisGeoCommands.GeoLocation<String>> results = stringRedisTemplate.opsForGeo().search(key,
                GeoReference.fromCoordinate(x, y),
                new Distance(5000),
                RedisGeoCommands.GeoSearchCommandArgs.newGeoSearchArgs().includeDistance().limit(end));
        //解析出店铺id
        if(results == null){
            return  Result.ok(Collections.emptyList());
        }
        List<GeoResult<RedisGeoCommands.GeoLocation<String>>> list = results.getContent();
        if (list.size() <= from){
            //没有下一页，直接结束
            return Result.ok(Collections.emptyList());
        }
        //截取从from到end的部分
        List<Long> ids = new ArrayList<>(list.size());
        Map<String, Distance> distanceMap = new HashMap<>();
        list.stream().skip(from).forEach(result -> {
            //获取店铺id
            String shopId = result.getContent().getName();
            ids.add(Long.valueOf(shopId));
            //获取距离
            Distance distance = result.getDistance();
            distanceMap.put(shopId, distance);
        });
        //根据id查询店铺
        String idStr = StrUtil.join(",", ids);
        List<Shop> shopList = query().in("id", ids).last("order by field (id, " + idStr + ")").list();
        for (Shop shop : shopList) {
            shop.setDistance(distanceMap.get(shop.getId().toString()).getValue());
        }
        //返回
        return  Result.ok(shopList);
    }
}
